(a) Field of the Invention
The present invention relates to a metal precursor powder, a method of manufacturing a conductive metal layer or pattern, and an electronic device including the same.
(b) Description of the Related Art
Metal electrodes have been utilized in various technical fields. Of these metal electrodes, as an example, an aluminum (Al) electrode is excellent in view of several electrical properties, such as electrical conductivity and work function, and is economical, and thus aluminum (Al) is utilized as an essential electrode material for various electronic, electric, energetic, and environmental devices.
More specifically, aluminum has the forth best electrical conductivity in metals on the earth, following silver, copper, and gold and has a very low work function, so that aluminum is very largely used in an electrode material requiring ohmic contact as well as an electrode material for charge transfer. Further, aluminum is very inexpensive. Therefore, aluminum may be a very attractive material as a next-generation electrode material.
However, since aluminum has high reactivity to moisture and oxygen, it is very difficult to subject aluminum to wet coating and printing. Currently, thin film types of electrodes are formed only through a vacuum deposition process other than in a technology according to which an electrode having a thickness of several micrometers or larger is formed by coating a paste on a rear electrode of a silicon solar cell through a screen printing process, the paste being composed of a micrometer-sized aluminum powder, and conducting heat treatment at a high temperature of 800° C. or higher.
The vacuum deposition process is very effective in implementing a pure aluminum layer having a desired thickness, but has problems in that the vacuum deposition apparatus is very expensive, the time and energy needed for maintaining a vacuum state are respectively long and high, and 70% or more of raw materials are lost. Considering these problems, in the case where large-area electrodes are needed like in 7th and 8th generation display devices, a vacuum chamber having a volume appropriate for the area is needed and the time and energy needed for maintaining a vacuum state of the vacuum chamber are further increased. Therefore, the vacuum deposition process may be very inappropriate in view of economic feasibility.
However, the wet printing and coating processes have an advantage in that an electrode with a desired shape can be formed in a very short time under a normal pressure atmosphere. Recently, many efforts to replace all technologies through the vacuum deposition process by the wet printing and coating process have been made.
However, most inks used in the wet printing and coating process are composed of an expensive gold or silver powder, of which the size is very large at a micrometer level, so that a high-temperature heating process is needed for contact and connection between powder particles.
As mentioned above, the paste composed of the aluminum powder having a 10 micrometer-level particle diameter is used. However, the aluminum powder, unlike gold or silver powder, has very large oxidation property and thus an oxidized film is formed on a surface of the aluminum powder. Therefore, in order to manufacture an electrically conductive layer by using an aluminum paste, it is necessary to conduct a heat treatment process at a high temperature of 800° C. or higher to thereby break the oxidized film on the surface of the aluminum powder and connect pure aluminum powder particles, which come out from the surrounding aluminum powder through the broken oxidized film.
That is, it is necessary to conduct heat treatment at a high temperature of 800° C. or higher in order to manufacture a conductive layer by using an aluminum paste. Therefore, it is impossible to apply aluminum as an electrode material in fields of recent organic electronic devices, flexible electronic devices, stretchable electronic devices, and the like, employing a substrate or an organic functional material, which is venerable to high temperatures.
In order to implement an aluminum layer having high electrically conductivity at a low temperature, recently published Korean Patent Registration Nos. 10-1021280 and 10-1195545 disclose developments of technology of realizing an aluminum layer having high electrical conductivity at room temperature to 150° C. by using a solution in which a material having various organic substances attached to an aluminum precursor, for example hydrogenated aluminum (AlH3), is dissolved in a particular solvent.
However, since the hydrogenated aluminum has very low solubility to the solvent, a significant amount of the aluminum precursor, hydrogenated aluminum, is precipitated from the aluminum precursor ink prepared according to the above patents in a very short time. Therefore, the concentration of the aluminum precursor ink cannot be maintained in a uniform state for a long time and thus the thickness of the finally formed aluminum layer is difficult to uniformly maintain, thus failing to uniformly maintain electrical characteristics of all the prepared aluminum layers.
Accordingly, there is need for a method of manufacturing a high-conductivity aluminum layer through wet printing and coating, the method being capable of solving the above problems and securing an aluminum precursor ink that is physically/chemically stable for a long time.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.